## Abstract

The leptonic branching ratios of the tau lepton have been determined from data collected by the OPAL detector in 1991 and 1992. From a sample of 27196 e^{+}e^{-}→τ^{+}τ^{-} candidates we find 7322 {Mathematical expression} and 7941 {Mathematical expression} candidates. Using efficiency and background estimates determined from a study of Monte Carlo events and control samples of data, the branching ratios {Mathematical expression}=(18.14±0.20±0.28)% and {Mathematical expression}=(17.48±0.18±0.23)% have been obtained. These new results have been combined with the published results for the 1990 OPAL data to yield the following branching ratios for data taken between 1990 and 1992: {Mathematical expression} These leptonic branching ratios are used with other properties of the muon and tau-lepton to test the universality of charged current leptonic couplings in these decays. The ratio {Mathematical expression} is calculated using our measured values of the leptonic branching fractions of the tau and tau lifetime from which a value of α_{s}(Q^{2}=M_{τ}^{2}) is extracted. The value of α_{s}(Q^{2}=M_{Z}^{2}) is obtained by Q^{2} evolution and agrees with the value from the Z^{0} line shape analysis.

Original language | English |
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Pages (from-to) | 543-554 |

Number of pages | 12 |

Journal | European Physical Journal C |

Volume | 66 |

Issue number | 4 |

DOIs | |

State | Published - 1 Dec 1995 |

Externally published | Yes |

## ASJC Scopus subject areas

- Physics and Astronomy (miscellaneous)